[optimizer] add div_scale for optimizers (#2117)

* [optimizer] add div_scale for optimizers

* [zero] use div_scale in zero optimizer

* fix testing error

colossalai/_C/fused_optim.pyi

@@ -11,7 +11,7 @@ def multi_tensor_sgd(chunk_size: int, noop_flag: Tensor, tensor_lists: List[List
     ...
 
 
-def multi_tensor_adam(chunk_size: int, noop_flag: Tensor, tensor_lists: List[List[Tensor]], lr: float, beta1: float, beta2: float, epsilon: float, step: int, mode: int, bias_correction: int, weight_decay: float) -> None:
+def multi_tensor_adam(chunk_size: int, noop_flag: Tensor, tensor_lists: List[List[Tensor]], lr: float, beta1: float, beta2: float, epsilon: float, step: int, mode: int, bias_correction: int, weight_decay: float, div_scale: float) -> None:
     ...
 
 

colossalai/kernel/cuda_native/csrc/colossal_C_frontend.cpp

@@ -17,8 +17,8 @@ void multi_tensor_adam_cuda(int chunk_size, at::Tensor noop_flag,
                             const float lr, const float beta1,
                             const float beta2, const float epsilon,
                             const int step, const int mode,
-                            const int bias_correction,
-                            const float weight_decay);
+                            const int bias_correction, const float weight_decay,
+                            const float div_scale);
 
 void multi_tensor_lamb_cuda(int chunk_size, at::Tensor noop_flag,
                             std::vector<std::vector<at::Tensor>> tensor_lists,
@@ -46,4 +46,4 @@ PYBIND11_MODULE(TORCH_EXTENSION_NAME, m) {
         "Computes and apply update for LAMB optimizer");
   m.def("multi_tensor_l2norm", &multi_tensor_l2norm_cuda,
         "Computes L2 norm for a list of contiguous tensors");
-}
\ No newline at end of file
+}

colossalai/kernel/cuda_native/csrc/multi_tensor_adam.cu

@@ -28,7 +28,7 @@ struct AdamFunctor {
       int chunk_size, volatile int *noop_gmem, TensorListMetadata<4> &tl,
       const float beta1, const float beta2, const float beta1_correction,
       const float beta2_correction, const float epsilon, const float lr,
-      adamMode_t mode, const float decay) {
+      adamMode_t mode, const float decay, const float div_scale) {
     // I'd like this kernel to propagate infs/nans.
     // if(*noop_gmem == 1)
     //   return;
@@ -79,6 +79,8 @@ struct AdamFunctor {
       }
 #pragma unroll
       for (int ii = 0; ii < ILP; ii++) {
+        if (div_scale > 0) r_g[ii] /= div_scale;
+
         if (mode == ADAM_MODE_0) {  // L2
           r_g[ii] = r_g[ii] + (decay * r_p[ii]);
           r_m[ii] = beta1 * r_m[ii] + (1 - beta1) * r_g[ii];
@@ -116,8 +118,8 @@ void multi_tensor_adam_cuda(int chunk_size, at::Tensor noop_flag,
                             const float lr, const float beta1,
                             const float beta2, const float epsilon,
                             const int step, const int mode,
-                            const int bias_correction,
-                            const float weight_decay) {
+                            const int bias_correction, const float weight_decay,
+                            const float div_scale) {
   using namespace at;
 
   // Handle bias correction mode
@@ -133,7 +135,7 @@ void multi_tensor_adam_cuda(int chunk_size, at::Tensor noop_flag,
       multi_tensor_apply<4>(BLOCK_SIZE, chunk_size, noop_flag, tensor_lists,
                             AdamFunctor<g_scalar_t_0, p_scalar_t_0>(), beta1,
                             beta2, bias_correction1, bias_correction2, epsilon,
-                            lr, (adamMode_t)mode, weight_decay);)
+                            lr, (adamMode_t)mode, weight_decay, div_scale);)
 
   AT_CUDA_CHECK(cudaGetLastError());
-}
\ No newline at end of file
+}

colossalai/nn/optimizer/cpu_adam.py

@@ -117,7 +117,7 @@ class CPUAdam(NVMeOptimizer):
         data.addcdiv_(exp_avg, denom, value=-step_size)
 
     @torch.no_grad()
-    def step(self, closure=None):
+    def step(self, closure=None, div_scale: float = -1):
         loss = None
         if closure is not None:
             with torch.enable_grad():
@@ -152,9 +152,10 @@ class CPUAdam(NVMeOptimizer):
                     self._pre_update(p, 'exp_avg', 'exp_avg_sq')
                     self.cpu_adam_op.step(state['step'], group['lr'], beta1, beta2, group['eps'], group['weight_decay'],
                                           group['bias_correction'], p.data, p.grad.data, state['exp_avg'],
-                                          state['exp_avg_sq'], -1)
+                                          state['exp_avg_sq'], div_scale)
                     self._post_update(p, 'exp_avg', 'exp_avg_sq')
                 elif target_device.type == 'cuda':
+                    assert div_scale == -1, "div_scale should remain default"
                     assert state['exp_avg'].device.type == 'cuda', "exp_avg should stay on cuda"
                     assert state['exp_avg_sq'].device.type == 'cuda', "exp_avg should stay on cuda"
 

colossalai/nn/optimizer/fused_adam.py

@@ -81,7 +81,7 @@ class FusedAdam(torch.optim.Optimizer):
         else:
             super(FusedAdam, self).zero_grad()
 
-    def step(self, closure=None, grads=None, output_params=None, scale=None, grad_norms=None):
+    def step(self, closure=None, grads=None, output_params=None, scale=None, grad_norms=None, div_scale: float = -1):
         """Performs a single optimization step.
 
         Arguments:
@@ -137,6 +137,6 @@ class FusedAdam(torch.optim.Optimizer):
 
             multi_tensor_applier(self.multi_tensor_adam, self._dummy_overflow_buf, [g_l, p_l, m_l, v_l], group['lr'],
                                  beta1, beta2, group['eps'], group['step'], self.adamw_mode, bias_correction,
-                                 group['weight_decay'])
+                                 group['weight_decay'], div_scale)
 
         return loss

colossalai/nn/optimizer/hybrid_adam.py

@@ -89,7 +89,7 @@ class HybridAdam(NVMeOptimizer):
         self._dummy_overflow_buf = torch.cuda.IntTensor([0])
 
     @torch.no_grad()
-    def step(self, closure=None):
+    def step(self, closure=None, div_scale: float = -1):
         loss = None
         if closure is not None:
             with torch.enable_grad():
@@ -126,7 +126,7 @@ class HybridAdam(NVMeOptimizer):
                     self._pre_update(p, 'exp_avg', 'exp_avg_sq')
                     self.cpu_adam_op.step(state['step'], group['lr'], beta1, beta2, group['eps'], group['weight_decay'],
                                           group['bias_correction'], p.data, p.grad.data, state['exp_avg'],
-                                          state['exp_avg_sq'], -1)
+                                          state['exp_avg_sq'], div_scale)
                     self._post_update(p, 'exp_avg', 'exp_avg_sq')
 
                 elif target_device.type == 'cuda':
@@ -146,6 +146,6 @@ class HybridAdam(NVMeOptimizer):
                 bias_correction = 1 if group['bias_correction'] else 0
                 multi_tensor_applier(self.gpu_adam_op, self._dummy_overflow_buf, [g_l, p_l, m_l, v_l], group['lr'],
                                      group['betas'][0], group['betas'][1], group['eps'], group_step, adamw_mode,
-                                     bias_correction, group['weight_decay'])
+                                     bias_correction, group['weight_decay'], div_scale)
         self._post_step()
         return loss

colossalai/nn/optimizer/zero_optimizer.py

@@ -10,10 +10,12 @@ from torch.optim import Optimizer
 from colossalai.amp.naive_amp.grad_scaler import DynamicGradScaler
 from colossalai.gemini.chunk import Chunk, ChunkManager
 from colossalai.logging import get_dist_logger
-from colossalai.nn.optimizer import ColossalaiOptimizer
+from colossalai.nn.optimizer import ColossalaiOptimizer, CPUAdam, FusedAdam, HybridAdam
 from colossalai.nn.parallel.data_parallel import ZeroDDP
 from colossalai.utils import disposable, get_current_device
 
+_AVAIL_OPTIM_LIST = {FusedAdam, CPUAdam, HybridAdam}
+
 
 class OptimState(Enum):
     SCALED = 0
@@ -62,6 +64,7 @@ class ZeroOptimizer(ColossalaiOptimizer):
                  **defaults: Any):
         super().__init__(optim)
         assert isinstance(module, ZeroDDP)
+        assert type(optim) in _AVAIL_OPTIM_LIST, "you should use the optimizer in the available list"
         self.module = module
         self.gemini_manager = module.gemini_manager
         self.chunk_manager: ChunkManager = self.gemini_manager.chunk_manager
@@ -162,21 +165,24 @@ class ZeroOptimizer(ColossalaiOptimizer):
         global_norm = math.sqrt(norm_sqr)
         return global_norm
 
-    def _unscale_and_clip_grads(self):
-        assert self.optim_state == OptimState.SCALED
+    def _get_combined_scale(self):
+        loss_scale = 1
+
+        if self.optim_state == OptimState.SCALED:
+            loss_scale = self.loss_scale
+            self.optim_state = OptimState.UNSCALED
 
-        combined_scale = self.loss_scale
+        combined_scale = loss_scale
         if self.clipping_flag:
             total_norm = self._calc_global_norm()
-            clip = ((total_norm / self.loss_scale) + 1e-6) / self.max_norm
+            clip = ((total_norm / loss_scale) + 1e-6) / self.max_norm
             if clip > 1:
-                combined_scale = clip * self.loss_scale
+                combined_scale = clip * loss_scale
 
-        for group in self.optim.param_groups:
-            for p in group['params']:
-                if p.grad is not None:
-                    p.grad.data.div_(combined_scale)
-        self.optim_state = OptimState.UNSCALED
+        if combined_scale == 1:
+            return -1
+        else:
+            return combined_scale
 
     @property
     def loss_scale(self):
@@ -199,12 +205,12 @@ class ZeroOptimizer(ColossalaiOptimizer):
             self._update_fp16_params()
             return
 
-        # unscale grads if scaled
-        if self.optim_state == OptimState.SCALED:
-            self._unscale_and_clip_grads()
+        # get combined scale. combined scale = loss scale * clipping norm
+        # so that gradient = gradient / combined scale
+        combined_scale = self._get_combined_scale()
         self.grad_scaler.update(found_inf)
 
-        ret = self.optim.step(*args, **kwargs)
+        ret = self.optim.step(div_scale=combined_scale, *args, **kwargs)
         self._register_states()
         self.zero_grad()
         self._update_fp16_params()

tests/test_optimizer/test_fused_adam_kernel.py

@@ -71,7 +71,7 @@ def test_adam(adamw, step, p_dtype, g_dtype):
         weight_decay = 0
 
         multi_tensor_applier(fused_adam, dummy_overflow_buf, [[g], [p], [m], [v]], lr, beta1, beta2, eps, step, adamw,
-                             True, weight_decay)
+                             True, weight_decay, -1)
 
         torch_adam_update(
             step,